Novel energetic sulfate salts and a process for their preparation

ABSTRACT

Novel energetic sulfate salts which form a eutectic with ammonium nitrate ntaining explosive formulations are disclosed. The eutectic quality of such formulations facilitates melt loading thereof. Two typical novel sulfate salts of the invention are 1-(2-ammonium sulfatoethyl)-2,4,6-trinitrobenzene and 1,3-Bis-2(2-ammonium sulfoethyl)-2,4,6-trinitrobenzene. Also disclosed is a method for the synthesis of such sulfate salts together also with a method for the synthesis of the necessary alkanol substituted trinitrobenzene derivative precursor.

The invention described herein may be manufactured, used and licensed byor for the Government for Governmental purposes without the payment tome of any royalties thereon.

This invention relates to certain eutectic forming novel energeticsulfate salts and to the eutectic explosive mixtures which contain suchsalts. This invention also relates in another aspect to the methods ofsynthesizing such salts. The sulfate salts contemplated by thisinvention are especially useful as a eutectic forming additive inexplosive formulations which contain ammonium nitrate.

By way of general background it should be noted that ammonium nitrate,whether by itself or in admixture with, e.g., ethylene diamine dinitrateand potassium nitrate is a well-known explosive. The melt loading ofcartridges, shells and other artillery items with ammonium nitrate (m.p.170 degrees (Celcius)) containing compositions is not only hazardous,but also wasteful of energy and requires especial attention toinsulation of the equipment involved.

Thus, there is a need for an additive which will form a eutectic withammonium nitrate, thereby significantly lowering the melting point ofthe resulting mixture. However, if the additive itself did not have thesame or comparable explosive energy output any advantage obtained from alowered melting point would be more than offset by a decreased energeticoutput of the resulting mixture.

The novel energetic sulfate salts of the present invention whichthemselves have considerable explosive energetic output of their own andwhich also form eutectics with explosive formulations containingammonium nitrate are ideally suited to meet this need.

Vender has reported that trinitrotoluene (TNT) will react withformaldehyde to form 1-(2-hydroxyethyl)-2,4,6-trinitrobenzene. See Chem.Abstracts 10, 1513 (1916). In the method suggested by Vender,1-(2-hydroxyethyl)-2,4,6-trinitrobenzene is obtained by heating TNT withformaldehyde in the presence of a base such as potassium bicarbonate orsodium hydroxide. A report upon subsequent research relating to theVender synthesis indicates that depending upon the base used or itsconcentration, there is either no reaction or excessive tar formation ora highly contaminated reaction product. See Journal of EnergeticMaterials vol. 2, 215-228 (Sept., 1984) published by Dowden, Brodman &Devine, Inc. The disclosure of the aforementioned publication is herebyincorporated in its entirety by this reference thereto.

It has now been surprisingly discovered that the Vender synthesisproceeds with less difficulty and with a higher product purity if thealkaline base (e.g., potassium bicarbonate, sodium hydroxide, sodiumcarbonate or potassium carbonate) is dissolved in the formaldehydereactant and the TNT reactant is dissolved in an organic solvent. Suchorganic solvent is preferably polar and tetrahydrofuran is eminentlysuitable.

The resulting 1-(2-hydroxyethyl)-2,4,6-trinitrobenzene is a typicalalkanol precursor for the synthesis of the sulfate salt compoundscontemplated by the present invention. The aforesaid presursor resultsin the synthesis of 1-(2-ammonium sulfatoethyl)-2,4,6-trinitrobenzenewhich is typical of one of the novel sulfate salts contemplated by thepresent invention.

According to the present invention, there is a novel2,4,6-trinitrobenzene derivative provided which contains R₁, R₂ and R₃attachments in the 1,3 and 5 positions respectively, wherein

(a) R₁ is a substituent selected from the group consisting of --CH₂ CH₂OSO₃ NH₄ and --CH₂ CH₂ CH₂ OSO₃ NH₄ ;

(b) R₂ is a substituent selected from the group consisting of --H,--CH₃,--CH₂ CH₃, --C(CH₃)₃, --CH(CH₃)₂, --CH₂ Pi, --CH₂ CH₂ Pi, --CH₂ CH₂ OSO₃NH₄ and --CH₂ CH₂ CH₂ OSO₃ NH₄ wherein Pi is an aryl, alkyl or alkylarylgroup of up to about 12 carbon atoms and

(c) R₃ is a substituent selected from the group consisting of --H,--CH₃, --CH₂ CH₃, --C(CH₃)₃, --CH(CH₃)₂, --CH₂ Pi, --CH₂ CH₂ Pi, --CH₂CH₂ OSO₃ NH₄ and --CH₂ CH₂ CH₂ OSO₃ NH₄ wherein Pi is an aryl, alkyl oralkylaryl group of up to about 12 carbon atoms.

In another aspect of the present invention, a method is provided for thesynthesis of the novel R₁ and R₂ disubstituted trinitrobenzenederivatives also included in the present invention (R₃ being --H in thatcase) from an alkanol precursor 2,4,6-trinitrobenzene compoundcontaining 1,3-substituents R₄ and R₅ wherein

(a) R₄ is selected from the group consisting of --CH₂ CH₂ OH and analkanol radical containing up to about 12 carbon atoms; and

(b) R₅ is selected from the group consisting of --H, an alkane radicalcontaining up to about 12 carbon atoms, --CH₂ CH₂ OH and an alkanolradical containing up to about 12 carbon atoms

which comprises the steps of

(1) reacting said alkanol precursor compound with a stoichiometricquantity of chlorosulfuric acid to form a supernatant liquid and a solidintermediate complex and

(2) reacting the solid intermediate complex with a stoichiometricquantity of ammonium hydroxide to yield a final compound according toclaim 3.

In yet another aspect of the present invention, a method is provided forthe synthesis of the alkanol presursor referred to immediately abovefrom TNT which comprises reacting a 2,4,6-trinitrobenzene derivativecompound containing 1,3-substituents R₆ and R₇ wherein

(i) R₆ is selected from the group consisting of --CH₃ and an alkaneradical containing up to about 12 carbon atoms; and

(ii) R₇ is selected from the group consisting of --H,--CH₃ and an alkaneradical containing up to about 12 carbon atoms

in an organic solvent solution with formaldehyde containing a basedissolved therein.

The following illustrative but non-limiting examples will aid in afurther understanding of the present invention. It will also be readilyapparent that in the succeeding examples no alkyl or alkylarylsubstituents are included in the available locations of the benzene ringof the resulting novel sulfate salt compound. However, in practice,there is no reason why an alkyl or alkylaryl substituent may not bepresent in any such available location or locations (with a suitablechoice of starting materials) so long as there is no undue interferencewith the energetic output of the resulting novel sulfate salt. A totalof up to 12 atoms, in addition to those already present on the benzenering and in the ammonium sulfatoethyl ligand or ligands represents theallowable limit of the size of such alkyl or alkylaryl substituentsbeyond which the energetic output of the resulting novel sulfate saltmay be adversely affected. In any specific case, the allowable limit ofthe size of any such alkyl or alkylaryl substituent can be determined bya person of ordinary skill in the art to which the present inventionpertains without undue experimentation.

EXAMPLE 1

To 13.0 g of 1-(2-hydroxyethyl)-2,4,6-trinitrobenzene slurried in 100 mlof methylene chloride, 7.0 g of chlorosulfuric acid dissolved in 50 mlof the same solvent is added with stirring and cooling. An oilseparates, which is stirred at room temperature for 15 minutes, duringwhich time it solidifies. The methylene chloride layer is decanted,fresh solvent is added to the solid residue and the solvent is againdecanted. The solid residue is dissolved in 250 ml of isopropanol.Aqueous ammonium hydroxide of 15% w/w strength is added to theisopropanol solution to slight excess. A heavy slurry is formed. Theslurry is filtered, the solid product washed with isopropanol and dried.16.8 g of the 1-(2-ammonium sulfatoethyl)-2,4,6-trinitrobenzene productrepresenting a 95% of theoretical maximum yield is obtained.

The product is a light tan solid. After recrystallization from anisopropanol-water mixture, it melts at 235 degrees Celcius withdecomposition. Elemental analysis of the product for C,H and S agreeswith the predicted theoretical proportions.

The infrared spectrum of the product shows absorption bandschracteristic of the presence of ammonium, sulfate and nitro groups.

The product was further tested upon a Mettler TA-2 Thermoanalyzer. Theproduct decomposes energetically, possibly even with ignition at 232degrees celcius, with a 60% loss of weight.

EXAMPLE 2

The product of Example 1 is mixed with an equal weight of an explosiveformulation comprising 46% w/w ammonium nitrate, 46% w/w ethylenediaminedinitrate and 8% w/w potassium nitrate. The resulting mixture melts at97 degrees Celcius. It is cooled to room temperature and reheated. Themelting point of the mixture now is 93 degrees Celcius indicating theformation of a eutectic.

EXAMPLE 3

To 6.0 g of the diol precursor mentioned in Example 1 slurried in 50 mlmethylene chloride, 6.0 g of chlorosulfuric acid dissolved in 50 ml ofmethylene chloride is added with stirring and cooling. The mixture isstirred for 30 minutes at room temperature and the supernatant liquid isdecanted. The insoluble material is then washed with a fresh portion ofmethylene chloride after which it is dissolved in 150 ml of isopropanol.Aqueous ammonium hydroxide of 15% w/w strength is added to theisopropanol solution to slight excess to yield a heavy precipitate,which is filtered and dried. The resulting solid product which is1,3-Bis-(2-ammmonium sulfatoethyl)-2,4,6-trinitrobenzene weighs 9.1 gpresenting 91% of theoretical maximum yield.

The product is recrystallized from an isopropanol-water mixture to yieldan off-white solid which melts at 287 degrees Celcius withdecomposition. Elemental analysis of the product for C and H agrees withthe predicted theoretical proportions.

The infrared spectrum of the product shows absorption bandscharacteristic of the presence of ammonium, sulfate and nitro groupsbeing similar as a whole to the infrared spectrum for the product ofExample 1.

EXAMPLE 4

The product of Example 3 is mixed with an equal weight of the explosiveformulation of Example 2. The resulting mixture melts at 102.6 degreesCelcius. It is cooled to room temperature and reheated. The meltingpoint of the mixture now is 95.8 degrees Celcius, indicating theformulation of a eutectic.

EXAMPLE 5

A solution of 0.6 g anhydrous potassium carbonate in 12.0 mlformaldehyde is added all at once with stirring to a hot solution of13.5 g of TNT in 75 ml of tetrahydrofuran. The mixture is refluxed withstirring for one hour, poured into 400 ml of water and acidified with asmall amount of hydrochloric acid. Upon standing overnight, crystalsform which are filtered and dried.

The yield of the resulting 1-(2-hydroxyethyl)-2,4,6-trinitrobenzene is14.0 g which represents 92% of the theoretical maximum yield.Chromatographic analysis shows a product purity of 99.6% with 0.3% TNTpresent as an unreacted impurity.

The product has a melting point of 110 to 112 degrees Celcius followingrecrystallization from isopropanol.

The infrared absorption spectrum of the product shows absorption bandsat the following frequencies (in reciprocal centimeters) which arediagnostic of the groups indicated in parentheses:

3560 (--OH), 3090, 1600, 1530 (--NO₂), 1350 (--NO₂), 1040 (--CH₂ OH),910, 740 and 720.

The scope of the present invention is further defined by and should beread in conjunction with the appended claims.

What is claimed is:
 1. A novel 2,4,6-trinitrobenzene derivativecontaining R₁, R₂ and R₃ attachments in the 1,3 and 5-positionsrespectively wherein(a) R₁ is a substituent selected from the groupconsisting of --CH₂ CH₂ OSO₃ NH₄ and --CH₂ CH₂ CH₂ OSO₃ NH₄ ; (b) R₂ isa substituent selected from the group consisting of --H,--CH₃, --CH₂CH₃, --C(CH₃)₃, --CH(CH₃)₂, --CH₂ Pi, --CH₂ CH₂ Pi, --CH₂ CH₂ OSO₃ NH₄and --CH₂ CH₂ CH₂ OSO₃ NH₄ wherein Pi is an aryl, alkyl or alkylarylgroup of up to about 12 carbon atoms and (c) R₃ is a substituentselected from the group consisting of --H, --CH₃, --CH₂ CH₃, --C(CH₃)₃,--CH(CH₃)₂, --CH₂ Pi, --CH₂ CH₂ Pi, --CH₂ CH₂ OSO₃ NH₄ and --CH₂ CH₂ CH₂OSO₃ NH₄ wherein Pi is an aryl, alkyl or alkylaryl group of up to about12 carbon atoms.
 2. A compound according to claim 1 wherein R₁ is asubstituent selected from the group consisting of --CH₂ CH₂ OSO₃ NH₄ and--CH₂ CH₂ CH₂ OSO₃ NH₄ ; R₂ is a substituent selected from the groupconsisting of --H, --CH₃, --CH₂ CH₃, --CH₂ CH₂ OSO₃ NH₄ and --CH₂ CH₂CH₂ OSO₃ NH₄ ; and R₃ is a substituent selected from the groupconsisting of --H, --CH₃, --CH₂ CH₃, --CH₂ CH₂ OSO₃ NH₄ and --CH₂ CH₂CH₂ OSO₃ NH₄.
 3. A compound according to claim 2 wherein R₁ is asubstituent selected from the group consisting of --CH₂ CH₂ OSO₃ NH₄ and--CH₂ CH₂ CH₂ OSO₃ NH₄ ; R₂ is a substituent selected from the groupconsisting of --H, --CH₃, --CH₂ CH₃, --CH₂ CH₂ OSO₃ NH₄ and --CH₂ CH₂CH₂ OSO₃ NH₄ and R₃ is --H.
 4. A compound according to claim 3 whereinR₁ is a substituent selected from the group consisting of --CH₂ CH₂ OSO₃NH₄ and --CH₂ CH₂ CH₂ OSO₃ NH₄ ; and R₂ is --H.
 5. A compound accordingto claim 4 wherein R₁ --CH₂ CH₂ OSO₃ NH₄.
 6. A compound according toclaim 3 wherein R₁ and R₂ are nonidentical substituents selected fromthe group consisting of --CH₂ CH₂ OSO₃ NH₄ and --CH₂ CH₂ CH₂ OSO₃ NH₄.7. A compound according to claim 3 wherein R₁ and R₂ are identicalsubstituents selected from the group consisting of --CH₂ CH₂ OSO₃ NH₄and --CH₂ CH₂ CH₂ OSO₃ NH₄.
 8. A compound according to claim 3 whereinR₁ and R₂ are both --CH₂ CH₂ CH₂ OSO₃ NH₄.
 9. An improved explosiveformulation which comprises ammonium nitrate in admixture with aneffective amount of the sulfate salt compound of claim 1 to result inthe formation of a eutectic mixture.
 10. The explosive formulation ofclaim 9 which comprises 23% w/w ammonium nitrate and 50% w/w of saidsulfate salt compound.
 11. The explosive formulation of claim 10 whichcomprises 23% w/w ammonium nitrate, 23% w/w ethylenediamine dinitrate,4% w/w potassium nitrate and 50% w/w of said sulfate salt compound. 12.The explosive formulation of claim 11 wherein said sulfate compound is1-(2-ammonium sulfatoethyl)-2,4,6-trinitrobenzene.
 13. The explosiveformulation of claim 11 wherein said sulfate compound is1,3-Bis-2(2-ammonium sulfatoethyl)-2,4,6-trinitrobenzene.
 14. A processfor making the eutectic mixture of claim 9 which comprises the stepsof(a) mixing together the ammonium nitrate with said sulfate saltcompound to form an intermediate mixture; and (b) heating theintermediate mixture to a temperature sufficient to cause liquefaction.15. A process for synthesizing the compound of claim 3 from an alkanolprecursor 2,4,6-trinitrobenzene compound containing 1,3-substituents R₄and R₅ wherein(a) R₄ is selected from the group consisting of --CH₂ CH₂OH and an alkanol radical containing up to about 12 carbon atoms; and(b) R₅ is selected from the group consisting of --H, an alkane radicalcontaining up to about 12 carbon atoms, --CH₂ CH₂ OH and an alkanolradical containing up to about 12 carbon atomswhich comprises the stepsof (1) reacting said alkanol precursor compound with a stoichiometricquantity of chlorosulfuric acid to form a supernatant liquid and a solidintermediate complex and (2) reacting the solid intermediate complexwith a stoichiometric quantity of ammonium hydroxide to yield a finalcompound according to claim
 3. 16. The process of claim 14 wherein thealkanol precursor is slurried in methylene chloride prior to reactionwith said chlorosulfuric acid.
 17. The process of claim 14 wherein thechlorosulfuric acid is dissolved in methylene chloride prior to reactionwith said alkanol precursor.
 18. The process of claim 14 wherein thereaction of the alkanol precursor with the chlorosulfuric acid isconducted at room temperature.
 19. The process of claim 14 wherein thealkanol precursor is reacted with the chlorosulfuric acid over a timeperiod of about 15 minutes to about 30 minutes.
 20. The process of claim14 wherein the solid intermediate complex is separated from thesupernatant liquid before it is reacted with ammonium hydroxide.
 21. Theprocess of claim 19 wherein the solid intermediate complex is washedwith a fresh portion of methylene chloride before it is reacted withammonium hydroxide.
 22. The process of claim 19 wherein the solidintermediate complex is dissolved in isopropanol before it is reactedwith ammonium hydroxide.
 23. The process of claim 14 wherein the solidintermediate complex is reacted with an excess quantity of ammoniumhydroxide.
 24. The process of claim 14 wherein the ammonium hydroxide isin aqueous solution of about 15% w/w strength.
 25. The process of claim14 wherein the final product compound is purified by filtration.
 26. Theprocess of claim 24 wherein the filtered final product compound isfurther purified by recrystallization from a liquid medium.
 27. Theprocess of claim 25 wherein the liquid medium is isopropanol.
 28. Theprocess of claim 24 wherein the liquid medium is a mixture ofisopropanol and water.
 29. A method for synthesizing the alkanolprecursor of claim 14 which comprises reacting a 2,4,6-trinitrobenzenederivative compound containing 1,3-substituents R₆ and R₇ wherein(i) R₆is selected from the group consisting of --CH₃ and an alkane radicalcontaining up to about 12 carbon atoms; and (ii) R₇ is selected from thegroup consisting of --H, --CH₃ and an alkane radical containing up toabout 12 carbon atomsin an organic solvent solution with formaldehydecontaining a base dissolved therein.
 30. The method of claim 29 whereinthe organic solvent is polar.
 31. The method of claim 29 wherein theorganic solvent is tetrahydrofuran.
 32. The method of claim 28 whereinthe dissolved base is selected from the group consisting of potassiumbicarbonate, sodium hydroxide, sodium carbonate, potassium carbonate andmixtures thereof.